Japan has stringent laws regarding the publication of pornography. Nagisa Ôshima was later charged with obscenity on publishing the screenplay, but was acquitted after a courtcase that dragged on for four years.
The film was not submitted for British classification until 1989 and the cinema release was then delayed until censor James Ferman was satisfied that the movie would not be liable for prosecution under the Obscene Publications Act. Previous showings had been limited to cinema clubs and even then the infamous scene where the young boy's penis is yanked by Sada had been removed entirely. For the 1989 submission Ferman used an optical zoom to reframe the offending shot and the film, by now deemed not obscene and safe from prosecution by a QC, was finally passed uncut for UK cinema in March 1991.
The trivia items below may give away important plot points.
The writing on Kichizo's chest, that Sada wrote using Kichizo's own blood, reads "Sada Kichi futari kiri" ("Sada and Kichi, just two of us together"). This was the actual writing seen on the real Kichizo's body when the police found his corpse on 19 May 1936.